The ulcer treatment seems to have done the trick. No more stomping, no more cranky antics in the cross ties. I've also taken to keeping the girth as loose as possible for as long as possible, and I think Willow appreciates that as well. She never used to care about girth tightening, but I think she has gotten more sensitive in the past year. All in all, she's a much happier horse than she's been for several weeks.
Willow's aloe vera supplement arrived this evening, so I started her on that. It's called Excel, and it's made by a vet in this neck of the woods. It contains aloe vera juice, slippery elm bark, and vitamin C. For anyone who's interested, in addition to the Excel, Willow's other supplements are: Grand Vite, Mare Magic, and ProBios. The barn I'm at has a forage-only feed option that I have Willow on; it consists of alfalfa, rice bran, and grass hay. The horses are fed four times a day, and I think that is so helpful in keeping them from developing any stall vices. I love my barn!